Two-stroke cycle engine

ABSTRACT

This engine has two crankshafts geared to one another to rotate in opposite directions about parallel axes, and two pistons, which reciprocate side-by-side in two cylinder bores that communicate with a common combustion chamber. The pistons are carried by a double yoke, which is connected by two rocker arms to two crankpins that are carried by flywheels coaxial with the crankshafts. Each pin is surrounded by an annular land that is integral with the associated flywheel. Each land passes through an arcuate recess in the associated rocker arm to guide the arm for limited pivotal movement about the crankpin during reciprocation of the yoke and pistons. The yoke carries a supercharger piston which controls the opening and closing of reed valves to supply fuel to a fuel chamber, which is periodically connected to the combustion chamber by a valve that is operated by a cam carried by one of the flywheels.

United States Patent [72] Inventor Van P. Combs Penfield, N.Y. [21] Appl. No. 817,014 [22] Filed Apr. 17,1969 [45] Patented Mar. 16, 1971 73] Assignee Bristol Associates, Inc.

Rochester, N.Y.

[54] TWO-STROKE CYCLE ENGINE 17 Claims, 6 Drawing Figs.

[52] US. Cl. 123/52, 74/25, 74/49, 91/411, 92/146, 123/53, 123/197 [51] Int. Cl ..F02b 75/18, F02b 75/32,Fl6h 21/18 [50] Field of Search 123/53 .(B1), 53 (A1), 53 (B), 53 (A), 52 (A), 53 (C), 197 (A1), 197 (A2), 197 (A3), 197 (MEL), 197; 92/146; 91/41 1; 74/49, 25, 50

[56] References Cited UNITED STATES PATENTS 1,358,954 11/1920 Holmstrom 123/53 1,512,404 10/1924 Burtnett 123/53 1,596,401 8/1926 Burtnett 123/53 2,117,700 5/1938 Burkhardt 123/53 Primary Examiner-Wendell E. Burns Attorney-B. Edward Shlesinger ABSTRACT: This engine has two crankshafts geared to one another to rotate in opposite directions about parallel axes, and two pistons, which reciprocate side-byside in two cylinder bores that communicate with a common combustion chamber. The pistons are carried by a double yoke, which is connected by two rocker arms to two crankpins that are carried by flywheels coaxial with the crankshafts. Each pin is surrounded by an annular land that is integral with the associated flywheel. Each land passes through an arcuate recess in the associated rocker arm to guide the arm for limited pivotal movement about the crankpin during reciprocation of the yoke and pistons. The yoke carries a supercharger piston which controls the opening and closing of reed valves to supply fuel to a fuel chamber, which is periodically connected to the combustion chamber by avalve that is operated by a cam carried by one of the flywheels.

Patented 1 March 16, 1971 3,570,459

5 Sheets-Sheet l I INVENTOR. G- 1 VAN P COMBS A TORNEY 5 Sheets-Sheet 2 INVENTOR.

VAN P COMES I ATTORNEY Patented arch 16, 1971 5 Shams-Sheet 3 IN VENTOR.

VAN P. COMBS jATTonnEY Patented March 16, 1971 5 Sheets-Sheet 4 R S OB M O E VC WP N A V FIG. 5

ATTORNEY Patented March 16, 1971 3,570,459

5 Sheets-Sheet 5 FIG. 6

INVENTOR. VAN. R .COMBS BY IATTORNEY TWG-STRGKIE CYCLE ENGINE This invention relates to a two cycle engine, and more particularly to improved crank and valve systems for a twostroke, internal combustion piston engine.

Most internal combustion engines utilize a wrist pin and connecting rod for connecting a reciprocable piston to a rotating crank pin to transfer drive between the piston and the crankshaft. A typical ratio of a connecting rod length to a crank radius is 4.33 to 1. It is generally regarded impractical, if not impossible, when using conventional wrist pin and connecting rod apparatus, to reduce this ratio below that of approximately 2 to 1. The advantages of being able to lower this ratio are a much more favorable cranking angle at the time the combustion pressure in a cylinder is highest, and more time for fuel intake and scavenging operations. Consequently, better and more efficient engine operation is achieved.

For further improvement of engine operation it is also desirable to incorporate in an internal combustion engine mechanism for supercharging the combustible fuel prior to its admission to the engines ignition chamber. Although efforts One object of this invention is to provide an improved two- "cycle piston engine, which is substantially more efficient and compact and less expensive than prior such engines.

Another object of this invention is to provide a novel crank mechanism for a piston engine of the two-cycle type.

A further object of this invention is to provide an improved supercharging mechanism for a two-cycle internal combustion engine.

A more specific object of this invention is to provide for an engine of the type described, a novel crank linkage, which will permit a substantial reduction in the ratio of the connecting rod length to crank radius.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a vertical sectional view taken through the crankcase and cylinders of a two cylinder,.two-cycle engine made in accordance with one embodiment of this invention, portions of the engine being broken away, and other portions thereof being shown in full;

FIG. 2 is a partial sectional view taken along the line 2-2 in FIG. 1 looking in the direction of the arrows, portions of the engine again shown in full;

FIG. 3 is a fragmentary sectional view taken along the line 3-3 in FIG. 1 looking in the direction of the arrows;

FIG. 4 is an enlarged, fragmentary sectional view taken along the line 4-4 in FIG. 3 looking in the direction of the arrows;

FIG. 5 is a partial sectional view similar to FIG. 1, but illustrating a modified form of this invention; and

FIG. 6 is a sectional view taken along the line 6-6 in FIG. 5 looking in the direction of the arrows.

Referring now to the drawings by numerals of reference, and first to the embodiment illustrated in FIGS. 1-4, denotes generally a hollow crankcase comprising a channel iron 21 secured on a base plate 22 with its web disposed in spaced, parallel relation to an end wall 23, and to a partition 24, which is integral with the end wall 23. Opposite sides of the crankcase are closed by plates 26 and 27; and the upper end thereof is sealed by a cylinder head 30.

Head 30 comprises two externally flanged castings 31 and 32, which are separated by a plurality of spaced, relatively thin metal plates 34. Registering openings in these castings and the plates 34 form in the head 30 a pair of spaced, parallel cylinder bores 35 and 36, the outer ends of which (the upper ends in FIGS. 1 and 2) are sealed by a head cap 37 that is secured in a recess in the outer casting 32. The outer ends of the bores 35 and 36 communicate with a firing chamber 38, which is a recess formed in cap 37.

. cap 37 to ignite fuel in the firing chamber 38.

Rotatably mounted in crankcase 20 are two, spaced, parallel crankshafts 42 and 43. Each of the shafts 42 and 43 is rotatably journaled intermediate its ends in spaced antifriction' bearings 45 (FIG. 2), which are secured in registering openings in the crankcase walls 23 and 24. Flywheels 46 and 47 are integral with the shafts 42 and 43, respectively, for rotation in side by side relation in the space between the crankcase walls 21 and 24. Y

Integral with the wheels 46 and 47, respectively, and radially offset like distances from their associated crankshaft axes, are two annular lands or rings 48 and 49. Also. secured to wheels 46 and 47, and projecting into the centers of the lands 48 and 49, are crankpins 51 and 52, respectively. Two small levers 54, 55 are pivotally mounted at one end on the crankpins 51, 52, respectively, and at their opposite ends project into notches 56, 57 are formed in the sector-shaped lower or inner ends of rocker arms 58, 59, respectively. Intermediate their ends the rocker arms 58, 59 have arcuate slots or grooves 61, 62, respectively, in which the lands 48, 49, respectively, slide. An arcuate strap bearing 63 is secured in each slot 61, 62 slidably to engage the outer peripheral surface of the associated land 48 or 49. 3

Remote from the crankpins 51 and 52 the rocker arms 58 and 59 have arcuate head portions 65 and 66, respectively, which are slidably secured by brackets 81 and 82 in arcuate sockets 72 and 73, respectively, that are formed in the lower end of a double yoke member 75. At its inner or lower end each bracket 81, 82 has a hooked-shaped lateral projection 85, 86, respectively, which extends slidably into one of two crescent-shaped openings 67, 68 formed in the upper ends of the rocker arms 58 and 59, respectively, thereby to hold the associated heads '65 and 66 of these arms in sliding, operative engagement with bearings 70. At their outer ends the brackets 81, 82 have trunnion portions 83, 84, respectively, which engage in openings formed in the spaced, parallel rods 76 and 77, which project from the yoke 75 into the cylinder bores 35 and 36, respectively. Connected to these rods 76 and 77 for reciprocation in the cylinder bores 35 and 36 are two pistons 78 and 79, respectively.

Keyed or otherwise secured to the shafts 42 and 43 to rotate between the walls 23 and 24 of the crankcase are meshing spur gears and 91 having identical numbers of teeth, so that the shafts 42 and 43 rotate in opposite directions at identical speeds. I

Secured in a recess in thecasting 31 medially of the cylinder bores 35 and 36 is a valve block 96 (FIGS. 1, 3 and 4) having. a central bore 97 that extends parallel to the bores 35 and 36. Fastened by screws 98 (FIG. 4) to opposite sides, respectively, of the block 96 are two end plates 100 and 101 (FIGS. 3 and 4). Plate 100 has on its inner side a pair of parallel grooves 102 and plate 101 has on its inside two parallel grooves 103. Secured by the screws 98 between the end plates 100, 101, respectively, and opposite sides, respectively, of the block 96 are flat mounting plates 105 and 106, respectively. Plate 105 has therethrough four ports 107, two of which register with one of the grooves 102 and the other two of which communicate with the outer groove 102, in plate 100. Similarly, plate 106 has there through four identically-shaped ports 106, two of which register with one of the grooves 103 in plate 101, and the other two of which communicate with the other groove 103 in this plate.

Secured intermediate their ends by screws 110 to plate 105, so that opposite ends thereof overlie and normally close the ports 107 in this plate, are two parallel, flexible reed valves 112. Secured intermediate their ends by screws 114 to the inside face of plate 106 (the left hand face as illustrated in FIG. 4) so that opposite ends thereof overlie and normally close the ports 108 in the plate 106, are two further reed valves 115.

The two upper ports 107 in the plate 105 register with two recesses 116 in block 96 and the two lower ports 107 in plate 105 communicate with recesses 117 in block 96. Two pairs 118, 121 of recesses similar to the pairs of recesses 116, 117, respectively, are formed in the opposite side of block 96.

As shown more clearly in FIG. 1, one end of each recess 116, 117 is rounded and likewise one end each of recesses 118, 121. The rounded ends of the recesses terminate short of the vertical center portion of the block 96. The upper ends of the recesses 116 and 118 communicate with the bore 97 in block 96 through shallow notches 119 and 120, which are formed in block 96 at diametrally opposite sides, respectively, of its bore 97. The lower ends of recesses 117, 121 similarly communicate through shallow notches 123, 125 with bore 97.

When the valves 112 are open, opposite ends thereof flex or bend away from the plate 105 into grooves 1.02 in the plate 100, so that the grooves 102 communicate through the ports 107 in plate 105, and the recesses 116, 117 in the block 96, with opposite ends of the bore 97. Similarly, when the valves 115 are open, their opposite ends flex or move away from the valve plate 106 and into the grooves 118, 121 in the block 96, so that the grooves 103 in the plate 101 communicate through the ports 108 in the plate 106, and the notches 120, 125 in block 96, with opposite ends of the bore 97.

The valves 112 and 115, which function as check valves, are operated by a piston 122, which is fixed to the upper end of a piston rod 124. The opposite end of rod 124 projects slidably through an opening in the plate 31, and is fixed to the yoke 75 midway between its arms 76 and 77. When the piston 122 is reciprocated, a combustible fuel, such as for example a mixture of air and propane, or air and gasoline vapor, is drawn alternately into opposite ends of the bore 97 from fuel lines 126 and 127 (FIGS. 3 and 4), which at one end are secured in the plate 101 to communicate with the ducts or grooves 103. Also during the reciprocation of the piston 122, the bore 97 is exhausted selectively out of opposite ends thereof to pipes 128 and 129, which at one end are secured in the plate 100 to communicate with the grooves 102, and which at their opposite ends are connected by conventional means (not illustrated) to one end ofa fuel line 130 (FIG. 2) that is secured to the upper casting 32.

The fuel line 130 communicates with the interior of a hollow, fuel intake housing 132 (FIGS. 1 and 3), which is secured in a recess in the casting 32 above the valve block 96.

The interior of housing 132 communicates with the firing chamber 38 through a sleeve 134, which is secured in registering openings in the adjacent walls of the casting 32 and housing 132. Adjacent the chamber 38 sleeve 134 has an internal, circumferential shoulder 136, which forms a seat for the head 137 of a conventional valve 138, that is mounted for limited reciprocation in the sleeve 136. Valve 138 has a stem portion, which is pivotally connected in conventional manner to one end ofa pivotal operating lever 140.

Lever 140 is fulcrumed intermediate its ends on a pin 142 that is carried by the legs of an inverted U-shaped bracket 143 that is secured to the housing 132 by a nut and bolt combination 145. The end of lever 140 remote from valve 138 is pivotally connected by a pin 146 to the furcated upper end (FIG. 3) of a cylindrical plug 147, which is slidably mounted in the upper end of sleeve 148 (FIGS. 2 to 4) for limited movement axially thereof. Sleeve 148, which is secured in the casting 31 adjacent valve housing 95, parallel to bore 97, extends at one end into housing 132, and at its opposite end into the top ofthe crankcase 20.

Fixed at one end to the plug 147 and projecting at its opposite end through sleeve 148 into the space between the crankcase walls 23 and 24, is an elongated actuating rod 150.

At its lower end rod 150 is pivotally connected by a pin 151 (FIGS. 1 and 3) to one end ofa lever 152, the opposite end of which is connected to a rocker shaft 154 (FIGS. 2 and 3). This latter connection is through a pin 155 (FIG. 3), opposite ends of which project radially from the shaft 154 into slots formed in one side of the lever 152. Opposite ends of shaft 154 are journaled in the crankcase walls 23 and 24 for rotation about an axis that extends parallel to the crank shafts 42 and 43, and to the pin 1.51. Shaft 154 projects through the crankcase wall 24, and is fixed to one end ofa pivotable arm 157 (FIG. 1), the opposite end of which engages the periphery of flywheel 47.

Fixed by a plurality of screws 158 to the flywheel 47 is a plate 159, which has an arcuate camming surface 160 that projects slightly beyond the periphery of the wheel 47 to engage, the free end of the arm 157 once per revolution of the wheel 47.

illustrated) in the sleeve 148, is a compression in the sleeve 148 (FIG. 3) with one end thereof engaged with the inner end of the plug 147, and with its opposite end seated on an internal shoulder (not illustrated) spring 162, which operates normally to hold the valve 138 closed. However, each time the arm 157 rides on the camming surface 160 of the flywheel 47, arm 157 is pivoted slightly counterclockwise in FIG. 1 so that the valve head 137 is lifted offits valve seat 136, thus momentarily placing the interior of the intake housing 132 in communication with the firing chamber 38. When the camming surface 160 has passed from beneath the follower 137, the spring 162 in the sleeve 148 returns the valve head 137 to its closed position (illustrated in FIG. 3).

At least one of the crankshafts 42 or 43, for example crankshaft 43, is connected in any conventional manner to a starting device (not illustrated), which is operable to impart initial rotation to the crankshaft 43.

Assuming that shaft 43 is initially rotated clockwise in FIG. 1 about its axis, its gear 91, will impart equal but opposite rotation to the shaft 42, and hence to its flywheel 46. The rotating flywheels 46 and 47 cause their associated crankpins 51, 52, and lands 48, 49, to be rotated about the axes of their respective crankshaft axes.

Assuming that this rotation commences when the pistons 78 and 79 are in their uppermost positions (illustrated in FIG. 1), the rotating lands 48, 49 cause the rocker arms 58,59, respectively, to be drawn downwardly in FIG. 1. Simultaneously the levers 54 and 55 impart slight turning torques to these rocker arms 58 and 59, so that the latter turn angularly relative to the lands 48 and 49.

While this is taking place, the connecting rods 81 and 82 draw the attached pistons 78 and 79 downwardly in the cylinder bores 35 and 36. By the time that the pins 51 and 52 have been rotated 90 from their starting positions the rocker arms 58 and 59 will have been angularly displaced relative to their associated lands 48 and 49, and to the connecting rod 81 and 82 approximately 25 from their original, vertical positions.

After the crankpins 51, 52 have rotated from their original positions, the rocker arms 58 and 59 continue to be drawn downwardly by the lands 43 and 49, and also commence to swing angularly back to vertical positions. They reach vertical positions when the crankpins 51 and 52 have been rotated l from the positions illustrated in FIG. 1. The yoke 75 and the pistons 78 and 79 will now have been drawn downwardly to their lowermost positions. 78 positions. This completes one stroke of the pistons 78 and 79. As the crankpins 51 and 52 continue to rotate, the rocker arms 58 and 59 swing upwardly toward their uppermost or zero positions, thus effecting the return of the yoke 75 and of the pistons 78 and 79 to their uppermost positions. At such time the two pistons 78 and 79 will have completed the second stroke of the two stroke cycle.

At the commencement of the above-described two stroke cycle of the pistons 78 and 79, the camming surface 160 is positioned from the cam follower arm 157, so that the cam 160 will not engage the follower 157, and thus actuate valve 130, until the flywheel 47 has been rotated 270, or three quarters of a revolution.

Also at the start of the cycle, the piston 122 will be in its uppermost position in bore 97, or substantially in the position illustrated in MG. 1. At this time the reed valves :12 and are closed, as is the exhaust mechanism (not illustrated) for the cylinder bores 35 and 36. Such an exhaust mechanism may be of the type illustrated, for example, in my U. S. Pat. No. 3,377,997, issued Apr. 16, 1968.

As piston 122 (FIGS. drawn inwardly on downward movement of the yoke 75 from the position illustrated in FIG. 1, a vacuum is created in the bore 97 above the piston. Consequently at this time the upper ends of the reed valves 112 FlGS. 1 and 3) are held closed by vacuum while the upper ends of the reed valves 115 are forced inwardly and opened to admit fuel from the lines 126 and 127 (FIG. 1) through the grooves or ducts 103, the upper (FIG. 3) ports 108 in plate 106, and the upper pair of notches 120 in the block 96 into the bore 97 above piston 122. Simultaneously, this movement of piston 122 also operates to compress any gas or fuel in bore 97 beneath the piston. The increased pressure developed in the lower end of the bore 97 causes the lower ends of the reed valves 112 to be opened, and maintains the lower ends of the reed valves 115 closed, so that any fuel or other gas in the lower end of the bore 97 beneath the piston 122 is forced outwardly through the notches 123 in the lower end of block 96, through the ports 107 in the lower end of plate 105, and through the grooves or ducts 102 and fuel lines 128 and 129 to the fuel line 130, and hence into housing 132.

When the piston 122 has reached its lowermost position, it will have compressed into the housing 132 all the fuel previously disposed in bore 97 beneath the piston 122 at the start of the cycle, and cam 160 will have been rotated only 180 clockwise from its position in FIG. 1, and consequently will not have yet actuated the follower 157.

As the flywheels 46, 47 and the cam 160 continue to rotate, however, and the yoke 75 begins to return piston 122 upwardly in bore 97, a vacuum is created in bore 97 beneath piston 122, and the fuel previously drawn into the bore 97 above the piston begins to be compressed. Consequently the lower ends of the reed valves 112 now close, while the lower ends of the valves 115 open, so that fuel is drawn from the lines 126 and 127, through the ducts 103, the lower ports 108 in the plate 106 and the lower notches 125 in block 96 into the bore 97 beneath the piston 122. On the other hand, the fuel that is being compressed in the bore 97 above the piston 122 maintains the upper ends of the reed valves 115 closed, and forces open the upper ends ofthe reed valves 112, so that the compressed fuel is forced through the notches 119 in the upper end of block 96, and through the upper slots 107 in the plate 105, and through the ducts 102 and the fuel lines 128 and 129 into intake housing 132.

When the piston 122 has returned approximately halfway upwardly in the bore 97 toward its initial or uppermost position, the camming surface 160 finally strikes the follower 157 momentarily to open the valve 137, so that the fuel compressed into housing 132 is admitted to the firing chamber 38. At this time pistons 78 and 79 will also have been returned only approximately halfway upwardly in their respective cylinder bores 35 and 36, so that the fuel admitted from housing 132 to the firing chamber 38, and consequently to the upper ends of the bores 35 and 30, is further compressed during the remaining advance of the pistons 78 and 79 toward their extreme upper positions. At such time the spark plug 40 is fired to ignite the compressed fuel in the firing chamber 38,

' to drive the pistons 78 and 79 downwardly and transfer their motion to the crankshafts 42 and 43 in the usual manner.

At the time that the valve 138 is opened momentarily by the cam 160, the piston 122 will have been returned only approximately halfway toward its uppermost position. Although the pressure in housing 132 is lowered momentarily with the opening of the valve 130, as soon as this valve closes, the pressure in housing 132 again begins to increase as a result of the continued upward movement of the piston 122. When piston 122 is finally returned to its uppermost position, the bore 97 beneath the piston 122 will be filled with fuel previously drawn in past the lower end of the reed valves 115. Upon the subsequent downward movement of the piston 122, this fuel will be forced into housing 132 in a manner similar to that described above.

From the foregoing it will be apparent that this invention provides a relatively simple, inexpensive and compact crank mechanism for a two-cycle piston engine. In practice an engine of the type illustrated has been constructed with a crank radius (i.e., the radial distance from the centerline of the crankshaft 42 or 13 to the centerline of the associated crankpin 51 or 52) of approximately 1.15 inches, and with an effective rocker arm (58 or 59) length of approximately 1.64 inches. Since the rocker arms 58 and 59 are equivalent to the pivotal connecting rods heretofore employed in engines of this type, the effective ratio of the connecting rod length (the rocker arm length) to the crank radius is approximately 1.42 to 1.0.

I-Ieretofore it has been possible with known crank mechanisms to obtain a ratio this low. Among the advantages of such a low ratio is the ability to provide a much more favorable cranking angle (i.e. the angular displacement of a rocker arm 58 or 59 from its vertical position), when the combustion pressures in the cylinder bores are highest. This results in a substantial increase in the time available to exhaust burned fuel from the cylinder bores, and to feed fresh fuel into the bores. Heretofore it was necessary to employ a valve-overlap type of construction to gain the necessary time to fill the cylinder bores with a supply of fuel between the end of an exhaust stroke and the beginning of the next intake stroke.

Also, with this novel construction, the pistons 78, 79 are moved away from top dead center faster than heretofore possible, which means that a cooler operating engine.

Not only is an engine of the type described herein suitable as an internal combustion engine; but also it is capable of being used in steam engines, or in compound cycle engines in which heated gases are admitted 'to the cylinders as the associated pistons are ready to leave top dead center. By using the double yoke 75 and the oscillating rocker arms 58 and 59, and counterrotating flywheels and crankpins, substantially all undesirable side thrust of the pistons is eliminated, thus reducing friction and wear on the engine.

A further advantage of applicants motor is the compactness thereof, which is afforded by the novel supercharging mechanism comprising piston 122 and the interconnected valve housings and 132. Supercharging devices on prior motors of the type described have tended to be extremely bulky and complex, and have not proved to be satisfactorily effective. Applicants novel construction, on the other hand, in addition to using very few moving parts, is housed substantially within the head of the engine to be protected from the elements, and to benefit from the heat generated in the head.

In the embodiment illustrated in FIGS. 5 and 6, a second head 30 is mounted on the crankcase 20 in opposition to the head 30. Since the head 30 and the linkages connecting its pistons to the crankshafts 42 and 43 are substantially identical to the corresponding parts previously described in connection with the head 30, like numerals primed will be employed to designate elements similar to those employed in the first embodiment. I

In thismodified embodiment, the pistons 78' and 79' (FIG. 5) of the head 30' are conmnected by a yoke 75, rods 81' and 82', rocker arms 55' and 59' and levers 54' and 55' to the crank pins 51 and 52, respectively, in a manner similar to that of the pistons 78 and 79 described in the first embodiment. However, the pistons 70 and 79' of head 30', and the abovedescribed linkages therefor, are connected to the crank pins 51 and 52, and hence to the flywheels 46 and 47, in opposition to the corresponding pistons 78 and 79, respectively, so that when the pistons 79 and 79 of the head 30 are in their outer or extended positions at the ends of their compression strokes (FIG. 5), the corresponding pistons 78 and 79', respectively, in head 30' are disposed in their innermost or retracted positions as shown, for example, in the lower part of FIG. 5. Conversely, when the pistons in the head 30' are in their outermost positions at the end of their compression strokes, the pistons 70 and 79 and the head 31) will be in their retracted or innermost positions.

As in the first embodiment, the yoke 7 5 associated with the head 30' has fixed to its midpoint a piston rod 121', which carries a piston 122' that is mounted for reciprocation in a second reed valve housing 96 that is carried in the head 30'. Fuel compressed by this second piston 122' is fed, as in the first embodiment, to a second intake housing 132 that is mounted in the head 30' for communication with the associated housing 96'. Housing 132 also contains a second valve 138', which is operable by a second lever 140' to control admission of fuel to the firing chamber 38 in head 30. The operating rod for this lever 140' passes through a second sleeve 143, which is mounted in head 30' in a manner similar to the first-mentioned sleeve 148 in head 30. An operating arm 157 is mounted on a second rocker shaft 154' for movement by a second cam 160'. Arm 157 overlies the periphery of the flywheel 47 at a point thereon diametrally opposite the follower 157 described in connection with the first embodiment.

Since in the modified engine of FIGS. and 6 the spark plug 40' in the head 30 is to be fired 180 out of phase with the spark plug 40 in the head 30, the same operating cam 160 (FIGS. 1 and 5), which was described in connection with the first embodiment, is utilized to operate both of the cam followers 157, 159' (FIGS. 5 and 6) of this modified engine. As will be apparent from examination of FIGS. 5 and 6, the cam 160 operates the respective followers at 180 intervals with respect to the rotation of the flywheel 47, so that when the pistons 78 and 79 in the head 30 are driven downwardly on an expansion stroke resulting from ignition of the fuel in the firing chamber 38 in head 30, the corresponding pistons 78 and 79' in the head 30 will be driven in unison outwardly in their associated cylinder bores; and when the fuel in the firing chamber 38 in the head 30' is ignited, the operation occurs in reverse.

The modified engine illustrated in FIGS. 5 and 6 has the advantages described above in connection with the embodiment of FIGS. 1 to 4; and moreover, it has the further advantage of increased horsepower output, resulting from the use of the two additional pistons 78' and 79' in the head 30' to augment the power imparted to the flywheels 46 and 47 by the pistons 78 and 79 in the head 30 during the expansion strokes of these last-mentioned pistons. This modified engine, therefore, is somewhat easier to start; and runs somewhat smoother during operation than does the first-described embodiment.

Iclaim:

1. An engine, comprising:

a rotatable crankshaft;

a flywheel secured to said shaft coaxially thereof;

a crankpin carried by said flywheel and having its axis radially offset from, and parallel to, the axis of said shaft;

a rocker arm pivotally connected at one end to said pin, and

having on its opposite end a curved bearing surface coaxial on an axis parallel to the axis of said pin;

a reciprocable member having on one end thereof a curved bearing surface slidably engaged with the first-named bearing surface coaxially thereof;

a piston attached to the opposite end of said reciprocable member for reciprocation transverse to the axis of said shaft; and

means connecting said arm to said reciprocable member to hold said curved bearing surfaces in sliding contact with one another during the reciprocation of said piston.

2. An engine as defined in claim 1, wherein:

said bearing surface on said arm is convex; and

said bearing surface on said member is concave.

3. An engine as defined in claim 1, wherein:

said arm has an arcuate groove disposed coaxially of the axis ofsaid pin; and

an annular land is integral with said wheel coaxially of said pin and seats slidably in said arcuate groove.

4. An engine as defined in claim 3, wherein a connecting lever is pivoted at one end on said pin and projects at its opposite end into a registering recess formed in said one end of said arm.

5. An engine as defined in claim 1, wherein:

said arm has therethrough an arcuate slot at least one side of which is located in spaced, coaxial relation to said curved surface on said arm; and

said connecting means comprising a rod fixed at one end to said member, and engaged at its opposite end in said slot to have sliding contact with said one side of said slot during the reciprocation of said piston.

6. An engine, comprising:

a rotatable crankshaft;

a flywheel secured to said shaft coaxially thereof;

an annular land integral with the face of said flywheel and having its axis radially offset from, and parallel to, the axis of said shaft;

a reciprocable member having in one end thereof a concave, arcuate recess;

a piston attached to the opposite end of said member for reciprocation in a direction transverse to the axis of said shaft;

a rocker arm having at one end a convexedly curved surface seated in said concave recess in said member, and having intermediate its ends an arcuate groove slidably seated over a portion of said land coaxially thereof; and

means connecting said arm to said member and operative to hold said curved surface and said groove on said arm in angular sliding contact with said concave recess and said land, respectively, during reciprocation of said piston.

7. An engine as defined in claim 6, including:

a crank pin secured to said wheel coaxially of said land; and

a lever pivoted at one end to said pin and projecting at its opposite end into a recess in the end of said arm remote from said curved surface.

8. An engine, comprising:

a hollow crankcase;

a head closing one end of said crankcase and having therein a pair of spaced, parallel cylinder bores;

a pair of crankshafts projecting into said crankcase, and mounted to rotate about a pair of spaced parallel axes transverse to the axes of said bores;

a pair of flywheels secured to said shafts for rotation therewith in said housing;

a pair of crankpins carried by said flywheels in equispaced, radially offset relation to the axes of rotation of said shafts;

a yoke reciprocable in said crankcase and having on one end thereofa pair of curved bearing surfaces;

a pair of pistons secured to the opposite end of said yoke for reciprocation in unison in said bores;

a pair of rocker arms pivotally connected at one end to said pins, and having at their opposite ends curved bearing surfaces slidably engaged with said bearing surfaces on said yoke; and

means connecting said arms to said yoke and operative to maintain said bearing surfaces on said arm in sliding contact with said bearing surfaces on said yoke during reciprocation on said pistons.

9. An engine as defined in claim 8, including means interconnecting said crankshafts, and operative to cause the rotation of one of said shafts to be imparted to the other so that said shafts rotate in opposite directions and at equal speeds.

10. An engine as defined in claim 8, wherein:

the bearing surfaces on said yoke are concave;

the bearing surfaces on said arms are convex; and

each pair of contacting bearing surfaces is coaxial of an axis parallel to the axes of said crankshafts.

11. An engine as defined in claim 8, wherein:

each of said flywheels has on one face thereof an integral,

annular land that surrounds the associated crankpin coaxially thereof; and

each of said arms has in one face thereof an arcuate groove which slidably overlies part of the land on the associated flywheel coaxially of the last-named land.

12. An engine as defined in claim 11, wherein:

each of said arms has thcrethrough an arcuate slot between its curved bearing surface and its arcuate groove; and

said connecting means comprises a pair of rods fixed at one end to said yoke, and having at their opposite ends laterally offset hook portions which project slidably into said slots in said arms to hold said bearing surfaces on said arms in contact with said bearing surfaces on said yoke.

13. An engine as defined in claim 11, wherein the ratio of the effective length of each of said rocker arms, to the radial distance between each of said pins and its associated crank axis, is less than 2 to 1.

M. An engine as defined in claim 8, including:

a valve housing mounted in said head between said cylinder bores and having an inlet port connected to a fuel supply, and an outlet port operatively connected to said cylinder bores;

a piston mounted in a bore in said housing, and connected to said yoke for reciprocation thereby axially in the lastnamed bore;

first valve means in said housing operative selectively to connect opposite ends of said last-named bore to said inlet port during reciprocation of the last-named piston; and

second valve means in said housing operative selectively to connect opposite ends of said last-named bore to said outlet port, during reciprocation of said last-named piston.

15. An engine as defined in claim 14, wherein:

said first valve means comprises at least one check valve mounted normally to close off said last-named bore from said inlet port, and operative, when the pressure of said fuel supply exceeds the pressure in said last-named bore, to open and connect said supply to said last-named bore; and

said second valve means comprises at least one check valve mounted normally to close off said last-named bore from said outlet port, and operative to connect said last-named bore to said outlet port, when the pressure at said outlet port is less than the pressure in said last-named bore.

16. An engine as defined in claim 14, including:

a second valve housing mounted in said head adjacent the first-named housing and having therein a chamber com municating with said outlet port in said first-named housa normally-closed valve mounted in said second housing for reciprocation between an open position in which it connects said chamberwith said cylinder bores, and a closed position in which it closes off said chamber from said cylinder bores; and

cam means operated by one of said crankshafts and connected to said valve momentarily to open said valve once during each revolution of said one crankshaft.

17. An engine as defined in claim 8, including:

a second head closing the opposite end of said crankcase and having therein a pair of spaced cylinder bores registering with the bores in the first-named head;

a second pair of pistons mounted to reciprocate coaxially in said bores in said second head; and

means for connecting said second pair of pistons to said flywheels for reciprocation in unison with the first-named pair of pistons, so that when said second pair of pistons are in their fully retracted positions in their associated cylinder bores the first-named pair of pistons are in their fully extended pistons in their bores, and vice versa. 

1. An engine, comprising: a rotatable crankshaft; a flywheel secured to said shaft coaxially thereof; a crankpin carried by said flywheel and having its axis radially offset from, and parallel to, the axis of said shaft; a rocker arm pivotally connected at one end to said pin, and having on its opposite end a curved bearing surface coaxial on an axis parallel to the axis of said pin; a reciprocable member having on one end thereof a curved bearing surface slidably engaged with the first-named bearing surface coaxially thereof; a piston attached to the opposite end of said reciprocable member for reciprocation transverse to the axis of said shaft; and means connecting said arm to said reciprocable member to hold said curved bearing surfaces in sliding contact with one another during the reciprocation of said piston.
 2. An engine as defined in claim 1, wherein: said bearing surface on said arm is convex; and said bearing surface on said member is concave.
 3. An engine as defined in claim 1, wherein: said arm has an arcuate groove disposed coaxially of the axis of said pin; and an annular land is integral with said wheel coaxially of said pin and seats slidably in said arcuate groove.
 4. An engine as defined in claim 3, wherein a connecting lever is pivoted at one end on said pin and projects at its opposite end into a registering recess formed in said one end of said arm.
 5. An engine as defined in claim 1, wherein: said arm has therethrough an arcuate slot at least one side of which is located in spaced, coaxial relation to said curved surface on said arm; and said connecting means comprising a rod fixed at one end to said member, and engaged at its opposite end in said slot to have sliding contact with said one side of said slot during the reciprocation of said piston.
 6. An engine, comprising: a rotatable crankshaft; a flywheel secured to said shaft coaxially thereof; an annular land integral with the face of said flywheel and having its axis radially oFfset from, and parallel to, the axis of said shaft; a reciprocable member having in one end thereof a concave, arcuate recess; a piston attached to the opposite end of said member for reciprocation in a direction transverse to the axis of said shaft; a rocker arm having at one end a convexedly curved surface seated in said concave recess in said member, and having intermediate its ends an arcuate groove slidably seated over a portion of said land coaxially thereof; and means connecting said arm to said member and operative to hold said curved surface and said groove on said arm in angular sliding contact with said concave recess and said land, respectively, during reciprocation of said piston.
 7. An engine as defined in claim 6, including: a crank pin secured to said wheel coaxially of said land; and a lever pivoted at one end to said pin and projecting at its opposite end into a recess in the end of said arm remote from said curved surface.
 8. An engine, comprising: a hollow crankcase; a head closing one end of said crankcase and having therein a pair of spaced, parallel cylinder bores; a pair of crankshafts projecting into said crankcase, and mounted to rotate about a pair of spaced parallel axes transverse to the axes of said bores; a pair of flywheels secured to said shafts for rotation therewith in said housing; a pair of crankpins carried by said flywheels in equispaced, radially offset relation to the axes of rotation of said shafts; a yoke reciprocable in said crankcase and having on one end thereof a pair of curved bearing surfaces; a pair of pistons secured to the opposite end of said yoke for reciprocation in unison in said bores; a pair of rocker arms pivotally connected at one end to said pins, and having at their opposite ends curved bearing surfaces slidably engaged with said bearing surfaces on said yoke; and means connecting said arms to said yoke and operative to maintain said bearing surfaces on said arm in sliding contact with said bearing surfaces on said yoke during reciprocation on said pistons.
 9. An engine as defined in claim 8, including means interconnecting said crankshafts, and operative to cause the rotation of one of said shafts to be imparted to the other so that said shafts rotate in opposite directions and at equal speeds.
 10. An engine as defined in claim 8, wherein: the bearing surfaces on said yoke are concave; the bearing surfaces on said arms are convex; and each pair of contacting bearing surfaces is coaxial of an axis parallel to the axes of said crankshafts.
 11. An engine as defined in claim 8, wherein: each of said flywheels has on one face thereof an integral, annular land that surrounds the associated crankpin coaxially thereof; and each of said arms has in one face thereof an arcuate groove which slidably overlies part of the land on the associated flywheel coaxially of the last-named land.
 12. An engine as defined in claim 11, wherein: each of said arms has therethrough an arcuate slot between its curved bearing surface and its arcuate groove; and said connecting means comprises a pair of rods fixed at one end to said yoke, and having at their opposite ends laterally offset hook portions which project slidably into said slots in said arms to hold said bearing surfaces on said arms in contact with said bearing surfaces on said yoke.
 13. An engine as defined in claim 11, wherein the ratio of the effective length of each of said rocker arms, to the radial distance between each of said pins and its associated crank axis, is less than 2 to
 1. 14. An engine as defined in claim 8, including: a valve housing mounted in said head between said cylinder bores and having an inlet port connected to a fuel supply, and an outlet port operatively connected to said cylinder bores; a piston mounted in a bore in said housing, and connected to said yoke for reciprocation thereby axially in the Last-named bore; first valve means in said housing operative selectively to connect opposite ends of said last-named bore to said inlet port during reciprocation of the last-named piston; and second valve means in said housing operative selectively to connect opposite ends of said last-named bore to said outlet port, during reciprocation of said last-named piston.
 15. An engine as defined in claim 14, wherein: said first valve means comprises at least one check valve mounted normally to close off said last-named bore from said inlet port, and operative, when the pressure of said fuel supply exceeds the pressure in said last-named bore, to open and connect said supply to said last-named bore; and said second valve means comprises at least one check valve mounted normally to close off said last-named bore from said outlet port, and operative to connect said last-named bore to said outlet port, when the pressure at said outlet port is less than the pressure in said last-named bore.
 16. An engine as defined in claim 14, including: a second valve housing mounted in said head adjacent the first-named housing and having therein a chamber communicating with said outlet port in said first-named housing; a normally-closed valve mounted in said second housing for reciprocation between an open position in which it connects said chamber with said cylinder bores, and a closed position in which it closes off said chamber from said cylinder bores; and cam means operated by one of said crankshafts and connected to said valve momentarily to open said valve once during each revolution of said one crankshaft.
 17. An engine as defined in claim 8, including: a second head closing the opposite end of said crankcase and having therein a pair of spaced cylinder bores registering with the bores in the first-named head; a second pair of pistons mounted to reciprocate coaxially in said bores in said second head; and means for connecting said second pair of pistons to said flywheels for reciprocation in unison with the first-named pair of pistons, so that when said second pair of pistons are in their fully retracted positions in their associated cylinder bores the first-named pair of pistons are in their fully extended pistons in their bores, and vice versa. 